Silicone oils having one or more poly(dimethylsilyloxy)-groups (PDMS-groups) in their polymeric chain are extensively used in the coating and ink industry as additives. The addition level of such additives is typically below 1 wt % of silicon oil based on the total liquid formulation. These additives impart a lower surface tension to the liquid, non-cured formulation. Thereby defects, such as crater formation, fish eyes, substrate dewetting and edge crawling can be reduced or even avoided. Moreover, a better surface flow can be achieved. As silicon-oils having PDMS groups normally tend to accumulate in the air-solid interface, they lead to an improved scratch resistance, anti-blocking behaviour, water repellency and water resistance of the dried coating and in particularly to surface slip of the dry coating film (slip additive).
The incorporation of silicon-oils having one or more PDMS groups into a polar formulation, like a water-based paint or ink, is difficult, in particular if the silicon-oil is rich in dimethylsilyloxy (DMS) groups, especially if the silicone oil is a pure polydimethysiloxane. The incompatibility of the hydrophobic polymer with the aqueous formulation leads to phase separation upon storage and hence to severe cratering of the coating once applied, and to haze after curing of the film.
Pure PDMS, called M-oil, consist of a linear arrangement of dimethylsilyloxy-groups, terminated on both ends by trimetylsilyloxy groups or Si-bound hydroxyl groups. M-oils are clear, colorless liquids at room temperature. They are characterized by the average number of repeating DMS units, by their molecular weight Mw, or by their viscosity, which depends on the lengths of the PDMS chain. These silicone oils are commercially available commodities.
The state of the art shows two technical solutions for including PDMS rich silicone oils, i.e. silicon-oil is rich in dimethylsilyloxy (DMS) group, as additives for aqueous systems:                (1) Providing an aqueous emulsion of the silicone oil. Typically large amounts of a nonionic or ionic surfactant are needed to prepare a physically stable aqueous emulsion of the silicon, the amount being up to 30 wt % of surfactant based on the silicone oil. Such emulsions can be stirred into the aqueous systems by applying low shear forces. However, a large amount of surfactant is thereby introduced into the formulation. This large amount of surfactants is known to lead to disadvantages like foaming problems, water sensitivity of the cured film, as well as surfactant migration, resulting smeary films, haze and fogging phenomena.        (2) Chemically modifying the PDMS rich silicone oil by introducing polar (and thus water compatible) polymer chains into the poly(dimethylsilyloxy) backbone. This route has a high complexity, as reactive sites, such as Si—H or Si—Cl groups, need to be introduced into the main poly(dimethylsilyloxy) chain, e.g. to the terminus (alpha-omega-silicones, block structures) or along the PDMS chains (comb structures), or combinations of the two. These reactive sites are then used for the chemical attachment of a water compatible, polar polymer, typically a polymer of ethylene oxide and/or propylene oxide repeating units. The chemical attachment is achieved via a condensation using OH-functionalities of the polar polymer, or addition reactions via Pt-catalysed hydrosilylation using an alpha-olefin functionality of the polar polymer. Thereby the resulting PDMS block or comb copolymers are rendered water dispersible or water soluble depending on the weight ratio and polarity of the introduced polar polymers. However, this simultaneously leads to a dilution of the surface active PDMS units in the formed polymer. Moreover, the surfactant character of the block or comb copolymer is strongly increased, helping the accumulation at the film-air interface on one side, but adding strongly to the foam and water sensitivity problems as in the case of PDMS emulsions.        
WO 2009153195 (Wacker Chemie) discloses nanoparticulate silicone organo copolymers in the form of aqueous polymer dispersions or polymer powders that can be redispersed in water where the copolymers are obtained by radically-initiated copolymerization in an aqueous medium, of one or more conventional monomers, such as vinyl esters, olefins and (meth)acrylic acid esters, with special linear mono(meth)-acrylate-functionalized poly(dimethylsiloxane), in the presence of at least one particle material being functionalized with ethylenically unsaturated, radically polymerizable groups. The material should provide coatings having excellent resistance e.g. against water weather impacts, attack by chemical agents and UV radiation; and low fouling tendency. However, the preparation of mono(meth)acrylate-functionalized poly(dimethylsiloxanes) is costly. As the PDMS groups are chemically attached to the inert polymer their effectiveness as surface additive in polar coating formulations is low.